The present invention relates to a semiconductor circuit and a semiconductor circuit. More specifically, the present invention relates to a semiconductor circuit and a semiconductor device for monitoring a battery voltage.
Recently, a high output battery with a large capacity has been widely used for driving a motor of a hybrid vehicle or an electric vehicle. In general, such a high output battery is formed of a plurality of batteries (battery cells) connected in series (as an example, a lithium-ion battery and the likes).
It has been known that a battery monitoring system is provided for monitoring and controlling a voltage of the battery cells of the high output battery. The battery monitoring system is composed of a measurement semiconductor circuit and a control semiconductor circuit, so that the battery monitoring system can monitor and control a voltage of the battery cells of the high output battery. When the battery monitoring system monitors and controls a voltage of the battery cells of the high output battery, various control signals (command signals) and data signals are exchanged between the measurement semiconductor circuit and the control semiconductor circuit. Patent Reference has disclosed a technology for reducing an influence on the command signals and the data signals due to external noises and the likes.    Patent Reference Japanese Patent Publication No. 2009-27916
FIG. 5 is a block diagram showing a configuration of a conventional semiconductor device 110 as the battery monitoring system. As shown in FIG. 5, the conventional battery monitoring system includes a battery 114 having a plurality of battery cell groups 115 and a semiconductor device 110 for measuring and controlling a voltage of battery cells 117 of the battery 114.
In the conventional battery monitoring system, a control semiconductor circuit 112 transmits a command (a signal) to a measurement semiconductor circuit 120. Accordingly, a cell voltage equalization process (equalizing the voltage of each of the battery cells 117) or a charging discharging control process (controlling charging and discharging of each of the battery cells 117) of the battery 114 are performed according to voltage information of each of the battery cells 117 obtained from the measurement semiconductor circuit 120.
In the conventional battery monitoring system, the measurement semiconductor circuit 120 is provided for each of the battery cell groups 115. In the following description, when it is necessary to differentiate each of the control semiconductor circuits 120, a subscript number is attached to the reference numeral. When the control semiconductor circuits 120 are referred collectively, the subscript number is omitted.
In the conventional battery monitoring system, the measurement semiconductor circuit 120 includes an IO circuit 122 for operating at a GND-VDD level on a low potential side and an IO circuit 132 for operating at a VCC-VCC2 level on a high potential side. Accordingly, the control semiconductor circuits 120 are configured to mutually exchange the command signals and the data signals such as measurement results without passing through a power source separation element. Further, the measurement semiconductor circuit 120 includes a logic circuit 124, an A/D conversion circuit 126, a cell selection circuit 128, a level shift circuit 130, and a voltage adjustment circuit 134.
In the conventional battery monitoring system, the measurement semiconductor circuit 120 further includes a VCC terminal connected to a power source line 113 of the battery 114; a VDD terminal for externally outputting an output voltage VDD of the voltage adjustment circuit 134; a VCC2 terminal connected to the measurement semiconductor circuit 120 on an upper stage; and Vn terminals (n=0 to n, n is an integer). The VCC terminal is provided for supplying a power source voltage to drive the cell selection circuit 128, the level shift circuit 130, and the voltage adjustment circuit 134, and for supplying a reference voltage of the IO circuit 132. The VCC2 terminal is provided for supplying a power source voltage of the IO circuit 132.
In the conventional battery monitoring system, in order to stabilize the power source voltage, an RC filter 119 is disposed between the VCC terminal and the power source line 113, and an LPF 118 is disposed between each of the Vn terminals and the power source line 113. A GND terminal is directly connected to the power source line 113.
In the conventional battery monitoring system, when the voltage of the battery cells 11711˜n1 is measured, the control semiconductor circuit 112 transmits the command signal to the semiconductor circuit 1201 for measuring the voltage of the battery cells 11711˜n1. When the command signal is input to the IO circuit 1221 of the semiconductor circuit 1201 through a communication terminal 1351, the logic circuit 1241 determines whether the command signal is the command signal for measuring the voltage of the battery cells 11711˜n1 connected to the semiconductor circuit 1201.
When the logic circuit 1241 determines that the command signal is not the command signal for measuring the voltage of the battery cells 11711˜n1 the logic circuit 1241 outputs the command signal as is to the level shift circuit 1301. The level shift circuit 1301 level shifts the command signal input at the GND-VDD level to the VCC-VCC2 level, and outputs the command signal to the semiconductor circuit 1202 at the upper stage through the communication terminal 1361.
When the logic circuit 1241 determines that the command signal is the command signal for measuring the voltage of the battery cells 11711˜n1 connected to the semiconductor circuit 1201, the cell selection circuit 1281 selects one of the battery cells 11711˜n1 whose voltage the command signal instructs to be measured. Then, the cell selection circuit 1281 outputs the data signal indicating the voltage of the one of the battery cells 11711˜n1 the control semiconductor circuit 112 through the transmission path through which the command signal is transmitted.
As described above, in the conventional semiconductor device 110, the command signal and the data signal indicating the voltage measurement result (the voltage of the battery cells 117) are exchanged through the communication terminals 135 and 136.
In the conventional battery monitoring system, an RC filter substantially equivalent to the RC filter 119 may be disposed between the GND terminal and the power source line 113, so that the GND potential does not fluctuate to a large extent. In this case, for example, when the battery cells 117 are charged, it is possible to supply the voltage to the GND terminal without a large fluctuation.
However, when the voltage of each of the battery cells 117 changes significantly while the battery cells 117 are being charged, the voltage input to the terminals V0 to Vn (referred to as Vo to Vn levels) changes significantly. Accordingly, a potential difference between the GND level and the Vo to Vn levels is shifted, or the GND level exceeds the Vo to Vn levels, thereby causing a false operation of the semiconductor circuit 120.
To this end, in the conventional semiconductor device 110 shown in FIG. 5, the GND terminal is directly connected to the power source line 113. Accordingly, even when the voltage of each of the battery cells 117 changes significantly while the battery cells 117 are being charged or a motor is driven, and the voltage input to the terminals V0 to Vn (referred to as Vo to Vn levels) changes significantly, it is possible to change the voltage supplied to the GND terminal of the semiconductor circuit 120. As a result, it is possible to prevent the GND level from exceeding the Vo to Vn levels, thereby preventing a false operation of the semiconductor circuit 120.
It is noted that, in the conventional semiconductor device 110 shown in FIG. 5, the GND terminal is directly connected to the power source line 113. Alternatively, an RC filter with a low property (a level lower than the RC filter 119) may be disposed between the GND terminal and the power source line 113
In the semiconductor circuit 120 of the conventional semiconductor device 110 shown in FIG. 5, it is difficult to reduce a noise in the following circumstance, thereby causing a problem.
In a hybrid vehicle or an electric vehicle driving, when a motor is driven, a load current is generated. Further, when a brake is applied, a charging current is generated in a regenerative brake system, so that the charging current is reused using the motor as a generator. Due to the load current or the charging current, the battery voltage tends to change significantly, and the change influences as the noise.
In the conventional semiconductor device 110 shown in FIG. 5, the change in the battery voltage may invert a logic level of the communication signal, thereby causing a false operation as shown in FIG. 6. FIG. 6 is a graph for explaining the false operation of the conventional semiconductor device 110.
In the conventional semiconductor device 110 shown in FIG. 5, when the load current and the like are generated in the battery cell group 1152, the battery voltage decreases by an internal resistance of the battery cells 117. Accordingly, a voltage V70 (the GND level (GND2) of the semiconductor circuit 1202) decreases, thereby decreasing the voltage.
As explained above, in the semiconductor circuit 120 of the conventional semiconductor device 110 shown in FIG. 5, the GND terminal is directly connected to the power source line 113. Accordingly, even when the voltage of each of the battery cells 117 changes significantly while the battery cells 117 are being charged or the motor is driven, and the Vo to Vn levels change significantly, it is possible to prevent the potential of the GND level from shifting relative to those of the Vo to Vn levels, and to prevent the GND level from exceeding the Vo to Vn levels, thereby preventing the false operation of the semiconductor circuit 120.
It is noted that when the GND terminal is directly connected to the power source line 113, the voltage supplied to the GND terminal of the semiconductor circuit 120 changes according to the change in the Vo to Vn levels. As a result, the voltage V70 (the GND level (GND2) of the semiconductor circuit 1202) changes as well. When the GND level (GND2) of the semiconductor circuit 1202 changes, a voltage VCC21 (the GND level (GND2) of the semiconductor circuit 1202) input into the VCC21 terminal of the semiconductor circuit 1201 changes as well.
As explained above, the RC filter 1191 is connected to the VCC1 terminal of the semiconductor circuit 1201. Accordingly, due to the filter effect of the RC filter 1191, a high frequency component is cut, and the voltage VCC1 does not change significantly. In sum, the voltage VCC21 does change and the voltage VCC1 does not change. Accordingly, when the voltage exceeds the threshold value, the logic level of the signal input into the IO circuit 1321 through the communication terminal 1361 is inverted, thereby causing the false operation.
In view of the problems described above, an object of the present invention is to provide a semiconductor circuit and a semiconductor device capable of solving the problems of the conventional semiconductor circuit and the conventional semiconductor device. In the present invention, it is possible to properly perform signal communication regardless of a change in a battery voltage due to a voltage variation.
Further objects and advantages of the invention will be apparent from the following description of the invention.